Suggestions for Centrifuge Purchase.
1.Machine Style Tabletop, portable and Floor stand type,
Tabletop is small to put into your table, it don't request a large space to put.
Portable type is very light and smaller than Tabletop one, it is more easy to bring it everywhere.
Floor stand type is always Large Capacity model, and request a space to put, it is better to ask the machine demision before you buy that.
if you only have small place to put this floor stand centrifuge.
2,Speed,
Normally we will separate all machine into Low speed(≤10000rpm) and High Speed(≥10000rpm), sometimes there will be other speed separation,
But you need to confirm with your doctor or your technical person that your application test requests how many rpm speed. 
this is the an important point
3,Refrigerated function,
Some special sample requests cool temperature during the centrifugation, then refrigerated centrifuge will be requested.
4,Application,
Different application will request for the different volume tubes and different speed, and other conditions,
so if you tell suppliers about your application, such as beauty, Hematocrit, Cell Smear and others, the supplier can suggest you suitable model according to their experience.
5,Rotator,
Max Rotator quantity to use in the machine, and the Rotator tube volume(how many ml), different types are with different price.
When you choose one machine, you should consider your possible applications, and check if these machine can be optional suitable rotators for the future usage, even you don't buy these rotators now.
Different Machine can be optional different rotator.